As far as I can tell, not all the states listed are calling for convention on the same merits, some are proposing adding one certain amendment and others are proposing adding a different one. The Indiana call is for a balanced budget amendment, the Maryland one (from what I can tell...?) is calling for limits on campaign donations.
If a convention is called upon, it's unlikely to result in all three fourths of the states agreeing on whatever proposals are out there.
I think most of this is just for political show, and not actually trying to amend the constitution. From what I can tell, the Constitution has never had an amendment added via three fourths of the state legislatures voting on it.
Just 27.